Sintering behaviour of celsian based ceramics obtained from the thermal conversion of (Ba, Sr)-exchanged zeolite A

Five different samples of (Ba, Sr)-exchanged zeolite A, exhibiting the same Na residual content within the experimental error, were prepared by cation exchange. These powders, with or without a previous thermal treatment, were cold pressed in an isostatic press to manufacture cylindrical compacts. Such compacts were subjected to various thermal cycles up to 1500 °C. The sintering and densification of these compacts was studied by determining linear shrinkages, mass variation, bulk density and porosity. All the compacts produced were totally composed by BaAl2Si2O8-SrAl2Si2O8 solid solutions occurring in the polymorph known as monoclinic celsian. Porosity lower than 0.1 % and bulk density higher than 95 % theoretical density were obtained. The problems arising in the sintering of compacts manufactured with zeolitic precursor are discussed and proper measures to solve them are suggested.